1. Field of the Invention
The present invention relates to a rehumidification filter for masks used for ventilation of dehumidified fluids.
2. Description of the Prior Art
Modifying the air that a human breathes has been a concern since the recognition that the human condition can be affected by modifying such air. Therefore, respiratory devices used to modify the air breathed under various circumstances, involving for example high-altitude flight and medical conditions, are abundant in the prior art.
Nevertheless, the devices heretofore proposed have not met with commercial success for a variety of reasons, including for example, extreme bulkiness, heavy weight, many moving parts, expensive non-disposable filters and tortuous passageways which cause extra expenditure of energy on the part of the human during both inhalation and exhalation.
For example, U.S. Pat. No. 3,099,987 issued Aug. 6, 1963 to Bartlett, Jr describes a respiratory apparatus intended primarily for use in military high-altitude applications, i.e. a flight-mask which sealing covers the mouth and nose of a user having a source of pressurized respirant which entry into the mask is controlled by valve structures. The apparatus includes a filter device containing a granular moisture transfer means, usually silica gel, whose container is wholly incorporated into the pathway of the inspired and expired fluids. The container is adapted at one end to be inserted into the mask, and on the other end detachably secured onto the valve structures. The container is further described to require screens secured to each end of the container for suitably confining the moisture exchange material therein. A valve foundation plate serves as the main connection structure between the mask and container structure and the valve structures. This plate has two large holes which serve to channel the expired and inspired fluids through their respective valves. This structure fails to provide a simple and inexpensive means of providing humidified respirant to the user.
U.S. Pat. No. 3,102,537 issued Mar. 7, 1963 to Bartlett, Jr also describes a flight-mask which is a combination valveless mask and a box-like structure containing valve and rehumidifying devices. Moisture transfer membranes, such as paper toweling having suitable capillary pores running throughout the thickness of the membranes, are interposed within the inspiratory and expiratory channels of the box-like structure. Again, this structure fails to provide a simple and inexpensive means of providing humidified respirant to the user.
U.S. Pat. No. 4,941,467 issued Jul. 17, 1990 to Takata describes a relatively simple humidification face-mask, similar in appearance to a surgical mask, intended for use in dry air environments such as airliner passengers must endure. The mask combines an inner mask member and an outer mask member between which a moisturizing pad is held. The moisturizing pad is adapted to carry a volume of water to humidify the air. A similar application is suggested in U.S. Pat. No. 4,705,033 issued Nov. 10, 1987 to Halfpenny, which describes a conical humidification face-mask containing a open-celled foam member also adapted to hold water across which inhaled air passes. However, the filtering structures are integral to the mask.
U.S. Pat. No. 2,468,383 issued Apr. 26, 1949 to Tiffany describes a nasal and sinus protector and warmer which is designed in appearance to resemble eyeglass frames wherein the nasal mask connects with tubing running contiguously with the brow of the face and which tubing terminates behind each ear. The terminus of the tubing contains an undefined filter. U.S. Pat. No. 5,386,825 issued Feb. 7, 1995 to Bates describes a respiratory breathing filter which is removably contained in an orally inserted apparatus through which the user breathes. Each of these filters are uniquely adapted for use with its device.
Several patents describe the use of metal netting, mesh or wire-gauze type structures for the purpose of heat and moisture exchange which operate on the principal of a counter-flow exchange in cold air conditions, whereby a loose or open structure of the metal mesh allows an almost entirely free passage of air yet recovers some heat and condensing humidity. U.S. Pat. No. 603,021 issued Apr. 26, 1898 to Dight describes a thermal inspirator which prevents the escape or ingress of air except through a tube which connects a heat storing chamber inclosed in the space under a hat and open to the air in such space with a nasal mask, through which the air is expelled and drawn in. The heat storing chamber is filled with a roll of metal wire-gauze. U.S. Pat. No. 3,326,214 issued Jun. 20, 1967 to McCoy describes a breath warming device using metal corrugated structures as heat exchange elements within a chamber. U.S. Pat. No. 4,136,691 issued Jan. 30, 1979 to Ebeling et al. describes a canister combined with a face-mask containing a heat exchanger made up of a continuous strip of wire netting wound helically to form a cylindrical netting roll. However, none of these devices teach the use of a disposable filter with a mask or describe a structure wherein air flow is substantially unrestricted while humidifying the air.
Therefore, despite the abundant variations of structure of devices which modify respiratory fluids, none of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.